During massage school my husband and I had a joke. “How’s your corrugator supercilii?” I would ask him after class. “Uh, I don’t know. You tell me,” he would oblige. I would then teach him about a funny little muscle with a really long name that moves the eyebrows. He has the most expressive eyebrows of anyone I know. (This feature has been passed on to our son, by the way.) The joke was a simple formula by which I could share a little obscure fact I found amazing about the body.
Which brings me to mechanoreceptors. “How are yours?” (want to play along?)
I loved learning about mechanoreceptors. They are sensory cells flung far and wide in the body which enable us to feel things like pressure. Their cousins allow us to feel heat, cold, degree of stretch, and where our limbs are in relation to our bodies. Distant cousins report to the brain taste, sound, light…you get the picture? All of these specialized receptors can also function as nociceptors – the guys who report pain. Too much pressure, cold or sound can all translate into pain.
Mechanoreceptors are found all over the body. Again, they register light touch, medium and deep pressure, vibration, stretch, even itch. The cells are found at different depths of the skin and fascia and are nestled inside tendons, ligaments and muscles. Clearly I’m a geek in writing about this, but I find it fascinating. Massage is all about stimulating these mechanoreceptor cells to fire like crazy at the brain. As I massage a super tight shoulder, kneading, tugging, and squeezing it, what I’m really doing is deforming these cells by mechanical pressure. And, unless I go too deep, too fast, the brain eats it up. “I’ll give you an hour to stop doing that!”
Have you ever remarked how good, how relaxing it feels to have your stylist or barber touch your hair, lift it, comb it, fluff it? Mechanoreceptors in action, baby! Each hair follicle has not only a nerve, but a muscle attached to it. Although we lose hair as we age, that’s still a lot of stimulus to the brain. It gives in and just relaxes. ~Sigh~ Cut off a few inches, I don’t care…
Sensory receptors have another trick up their sleeve. The concentration of sensory nerves varies throughout the body. Places like the fingertips and tip of the tongue are high density, like Tokyo or Mexico City. On the back of the leg the brain cannot distinguish 2 points of contact up to 2 inches apart as unique. They feel like the same point. Think Montana or Utah perhaps. The nervous system splurges in some places and cuts corners in Utah.
So, next time you get a massage think for a moment of what’s happening on a cellular level. Before you drift into la-la land, appreciate the nervous system feedback loop that can distinguish so many different stimuli, assigning each its importance appropriately. Truly amazing!